8 ms·

The biggest problem is lightning strikes hitting the cable. The phase wouldn’t matter - and even different earthing wouldn’t matter as long as you only connect

The biggest problem is lightning strikes hitting the cable. The phase wouldn’t matter - and even different earthing wouldn’t matter as long as you only connect any shield at one end. But fibre is so much more versatile if you’re running new cables (unless you want to run power)

repiret 4y ago
Last summer the local cable company replaced all their cables in town in order to begin offering digital cable and internet service. I was flabbergasted that they they spent all that money on linemen but still ran coax rather than fiber. As far as I can tell talking to their linemen, its not even FTTN, just FTT-central-office. Assuming its not run by morons, which I'll accept is a bit of a stretch for a cable company, there must be some other reason to not run fiber for new installations.
- jcrawfordor 4y ago
  DOCSIS is capable of 3gbps over coaxial cable and there is more room to improve, so fiber doesn't have a significant advantage in terms of possible bandwidth. Because DOCSIS was designed to operate on the cable network, which was designed to reach a very large number of homes, the architecture of the system tends to be more cost-effective than fiber. The fiber equivalent of a cable-like topology, and what is used by fiber ISPs, is PON, but PON is actually relatively limited in terms of both range and number of service points compared to DOCSIS on cable. A typical PON installation requires more field equipment to serve the same customers at the same rate compared to DOCSIS. This is made worse by the issue of power distribution: the field equipment for DOCSIS consists of distribution amplifiers which are powered over the coaxial cable itself, allowing the battery-backed power supplies to be placed at convenient locations. There's not really any equivalent of this for PON, so extending PON networks beyond a single loop (depends a lot but typically a few KM and <100 customers) requires an OLT which is relatively large and needs separate power provisioned. You can put OLTs in serving area cabinets but this is costlier compared to cable equipment. Another major factor is the customer premises: most homes already have coaxial cable distribution installed that is either compatible with DOCSIS 3 or can be made compatible with DOCSIS 3 by replacing the distribution amplifier or passive tap, which is a fairly cheap and fast operation. Installing PON to customers requires getting fiber to their house, and then either an outdoor ONT (troublesome from a maintenance perspective) and ethernet into the building or fiber into the building. The equipment here doesn't necessarily cost much but the labor of running new lines into customer homes is substantial and makes signing up new customers much higher-friction. Most of the time when a cable provider upgrades to introduce DOCSIS 3 for digital voice and internet they aren't really replacing any cable anyway, just distribution amplifiers and nodes. The cost of this work is significantly lower than running new cable and it doesn't require new pole attachment agreements etc. In general, in urban environments with existing cable TV plant there are few upsides to fiber. Urban fiber in existing areas is usually only cost effective when it's a new ISP competing with the cable company. Finally, most DOCSIS networks are in a process of transitioning from CMTS (cable modem termination system, the upstream end) in the cable headend to a compact serving area CMTS at each amplifier point. This is called "Node+0" architecture, meaning there is a fiber node and then zero distribution amplifiers before the customer. One of the nice things about the cable "HFC" or hybrid fiber/coaxial network is that it is relatively easy to make this transition progressively as you sign up additional customers, since CMTS nodes have been made very small. PON is less forgiving this way and requires more up-front capacity planning, especially since network expansion means the permitting process on relatively large curb cabinets or enclosures.
- Aloha 4y ago
  Cost and Fragility. You can push around 1GHz of bandwidth on the normal hardline-feed line with taps system cable uses, each node is designed to pass by a certain number of households. Coax is.. cheap, forgiving, easy to terminate, and inexpensive to replace - Fiber is more expensive, unforgiving, and much harder to terminate.
  - GreyStache 4y ago
    Regarding the termination: our local fiber provider handles the termination with some optical precision connector (forgot the name). Both to the sunken-in-sidewalk multiplexer and in the home to the optical termination point (both gpon). So for mass deployments fiber connections do not require fibre welds are not required. I have to see it play out in practice and I'm not a fan of the idea that one telco controls controls (ie stifles competition) in a gpon scenario. The conduit has recently been placed in our street, so "soon"...
    - Aloha 4y ago
      I'm still a fan for cost reasons of FTTN, because I think with Coax in the last mile, you can deliver fantastic performance, so long as you're not also trying to delivery video too. Furthermore if you actually run Coax in duct for buried circuits, its easy to replace with fiber later.
      - bayindirh 4y ago
        Our telco converted all its infra to FTTN via fiber. So, I've actually have fiber connection up to the front of my building, then it's terminated and distributed via VDSL to the street. I have a 50/8 mbps connection at home and, it gives all the performance it can give. The telco keeps the speeds a bit higher to handle VDSL overhead, so we have a real 50/8 mbps IP connection at premises. I'd rather not rewire my home and use existing equipment (which can handle 350mpbs), rather than bringing in fragile fiber into the home.
        xenadu02 4y ago
anonymousiam 4y ago
Lots of comments about lightning, but I believe you are referring to a "ground loop" where the ground/neutral at one site is offset from that of a different site tens or hundreds of meters away. This is why all commonly used RJ-45 Ethernet connections use differential signalling and have the tx/rx pairs isolated by transformers. (Note that PoE Ethernet can still create similar problems if one is not careful.) Here's a relevant news article about a lawsuit related to this phenomenon: https://easyreadernews.com/edison-stray-voltage/ https://easyreadernews.com/edison-stray-voltage/ https://www.dailybreeze.com/2013/03/19/redondo-beach-woman-awarded-4-million-in-edison-lawsuit-over-stray-electricity/ https://www.dailybreeze.com/2013/03/19/redondo-beach-woman-a... https://www.nydailynews.com/news/national/woman-wins-4m-verdict-stray-electricity-article-1.1294855 https://www.nydailynews.com/news/national/woman-wins-4m-verd...
upofadown 4y ago
... also lightning strikes hitting the ground somewhere in the area. That can induce large voltage differences between the power grounds on the buildings. The voltage difference might be large enough to arc across any isolation provided by the physical network implementation.
- kevin_thibedeau 4y ago
  My neighbor's house was hit by lightning last year and it took out the ethernet ports on two of my devices. Nothing else was affected though. Those devices still work. They're on a PoE switch (though not using PoE) so that may have been part of the cause.
madaxe_again 4y ago
Then you just install a lightning arrestor on your comms circuit - I have a mast way up the hill to provide our connectivity here, and use one on the Ethernet line down to prevent issues (like a house fire) from a strike.
- Aloha 4y ago
  You have to assume a direct hit by lightening will fry your hardware, period, full stop - proper grounding and lightning protection however will mean that the hardware does not catch fire.
  - Animats 4y ago
    There are lightning protectors that will absorb a direct lightning strike. Most antennas on hilltops and tall buildings have them. They take lightning strikes routinely. Here's some ARRL material on lightning protection.[1] It's not difficult, but it's not miniature. A classic design was a soup-can sized device with a coax connector on each end and a hulking big ground connection on the can. Inside was a spark gap with dime-sized silver contacts, and a few turns of copper busbar as an inductor to smooth out the spike that got past the spark gap. That goes where the cable enters the building. Similar units today tend to be smaller. There will still be serious metal boxes.[1] You need a serious ground. As in hulking big copper cable to a long ground rod. Grounding to a pipe is no longer allowed; there might be plastic pipe somewhere in the system, either now or in the future. The next stage is a "central office protector". This is a gas tube with three terminals - both sides of the line, and ground. So it's an enclosed spark gap in an inert gas. An overvoltage will ionize the gas and short it to ground. Telco central offices have one of those on each line. They're plug-in devices that sometimes have to be replaced. There's a lot of obviously fake stuff on eBay and Amazon in this area. 2D logos superimposed on curved surfaces, even. There's a standard, UL 497B. If it doesn't have that certification, don't buy. [1] https://www.polyphaser.com/search?Category=Data+Surge+Protectors&sort=y&view_type=grid https://www.polyphaser.com/search?Category=Data+Surge+Protec... [1] http://www.arrl.org/lightning-protection http://www.arrl.org/lightning-protection
    - 4y ago

repiret 4y ago

Last summer the local cable company replaced all their cables in town in order to begin offering digital cable and internet service. I was flabbergasted that they they spent all that money on linemen but still ran coax rather than fiber. As far as I can tell talking to their linemen, its not even FTTN, just FTT-central-office. Assuming its not run by morons, which I'll accept is a bit of a stretch for a cable company, there must be some other reason to not run fiber for new installations.

jcrawfordor 4y ago
DOCSIS is capable of 3gbps over coaxial cable and there is more room to improve, so fiber doesn't have a significant advantage in terms of possible bandwidth. Because DOCSIS was designed to operate on the cable network, which was designed to reach a very large number of homes, the architecture of the system tends to be more cost-effective than fiber. The fiber equivalent of a cable-like topology, and what is used by fiber ISPs, is PON, but PON is actually relatively limited in terms of both range and number of service points compared to DOCSIS on cable. A typical PON installation requires more field equipment to serve the same customers at the same rate compared to DOCSIS. This is made worse by the issue of power distribution: the field equipment for DOCSIS consists of distribution amplifiers which are powered over the coaxial cable itself, allowing the battery-backed power supplies to be placed at convenient locations. There's not really any equivalent of this for PON, so extending PON networks beyond a single loop (depends a lot but typically a few KM and <100 customers) requires an OLT which is relatively large and needs separate power provisioned. You can put OLTs in serving area cabinets but this is costlier compared to cable equipment. Another major factor is the customer premises: most homes already have coaxial cable distribution installed that is either compatible with DOCSIS 3 or can be made compatible with DOCSIS 3 by replacing the distribution amplifier or passive tap, which is a fairly cheap and fast operation. Installing PON to customers requires getting fiber to their house, and then either an outdoor ONT (troublesome from a maintenance perspective) and ethernet into the building or fiber into the building. The equipment here doesn't necessarily cost much but the labor of running new lines into customer homes is substantial and makes signing up new customers much higher-friction. Most of the time when a cable provider upgrades to introduce DOCSIS 3 for digital voice and internet they aren't really replacing any cable anyway, just distribution amplifiers and nodes. The cost of this work is significantly lower than running new cable and it doesn't require new pole attachment agreements etc. In general, in urban environments with existing cable TV plant there are few upsides to fiber. Urban fiber in existing areas is usually only cost effective when it's a new ISP competing with the cable company. Finally, most DOCSIS networks are in a process of transitioning from CMTS (cable modem termination system, the upstream end) in the cable headend to a compact serving area CMTS at each amplifier point. This is called "Node+0" architecture, meaning there is a fiber node and then zero distribution amplifiers before the customer. One of the nice things about the cable "HFC" or hybrid fiber/coaxial network is that it is relatively easy to make this transition progressively as you sign up additional customers, since CMTS nodes have been made very small. PON is less forgiving this way and requires more up-front capacity planning, especially since network expansion means the permitting process on relatively large curb cabinets or enclosures.
Aloha 4y ago
Cost and Fragility. You can push around 1GHz of bandwidth on the normal hardline-feed line with taps system cable uses, each node is designed to pass by a certain number of households. Coax is.. cheap, forgiving, easy to terminate, and inexpensive to replace - Fiber is more expensive, unforgiving, and much harder to terminate.
- GreyStache 4y ago
  Regarding the termination: our local fiber provider handles the termination with some optical precision connector (forgot the name). Both to the sunken-in-sidewalk multiplexer and in the home to the optical termination point (both gpon). So for mass deployments fiber connections do not require fibre welds are not required. I have to see it play out in practice and I'm not a fan of the idea that one telco controls controls (ie stifles competition) in a gpon scenario. The conduit has recently been placed in our street, so "soon"...
  - Aloha 4y ago
    I'm still a fan for cost reasons of FTTN, because I think with Coax in the last mile, you can deliver fantastic performance, so long as you're not also trying to delivery video too. Furthermore if you actually run Coax in duct for buried circuits, its easy to replace with fiber later.
    - bayindirh 4y ago
      Our telco converted all its infra to FTTN via fiber. So, I've actually have fiber connection up to the front of my building, then it's terminated and distributed via VDSL to the street. I have a 50/8 mbps connection at home and, it gives all the performance it can give. The telco keeps the speeds a bit higher to handle VDSL overhead, so we have a real 50/8 mbps IP connection at premises. I'd rather not rewire my home and use existing equipment (which can handle 350mpbs), rather than bringing in fragile fiber into the home.
      - xenadu02 4y ago

anonymousiam 4y ago

Lots of comments about lightning, but I believe you are referring to a "ground loop" where the ground/neutral at one site is offset from that of a different site tens or hundreds of meters away. This is why all commonly used RJ-45 Ethernet connections use differential signalling and have the tx/rx pairs isolated by transformers. (Note that PoE Ethernet can still create similar problems if one is not careful.) Here's a relevant news article about a lawsuit related to this phenomenon: https://easyreadernews.com/edison-stray-voltage/ https://easyreadernews.com/edison-stray-voltage/ https://www.dailybreeze.com/2013/03/19/redondo-beach-woman-awarded-4-million-in-edison-lawsuit-over-stray-electricity/ https://www.dailybreeze.com/2013/03/19/redondo-beach-woman-a... https://www.nydailynews.com/news/national/woman-wins-4m-verdict-stray-electricity-article-1.1294855 https://www.nydailynews.com/news/national/woman-wins-4m-verd...

upofadown 4y ago

... also lightning strikes hitting the ground somewhere in the area. That can induce large voltage differences between the power grounds on the buildings. The voltage difference might be large enough to arc across any isolation provided by the physical network implementation.

kevin_thibedeau 4y ago
My neighbor's house was hit by lightning last year and it took out the ethernet ports on two of my devices. Nothing else was affected though. Those devices still work. They're on a PoE switch (though not using PoE) so that may have been part of the cause.

madaxe_again 4y ago

Then you just install a lightning arrestor on your comms circuit - I have a mast way up the hill to provide our connectivity here, and use one on the Ethernet line down to prevent issues (like a house fire) from a strike.

Aloha 4y ago
You have to assume a direct hit by lightening will fry your hardware, period, full stop - proper grounding and lightning protection however will mean that the hardware does not catch fire.
- Animats 4y ago
  There are lightning protectors that will absorb a direct lightning strike. Most antennas on hilltops and tall buildings have them. They take lightning strikes routinely. Here's some ARRL material on lightning protection.[1] It's not difficult, but it's not miniature. A classic design was a soup-can sized device with a coax connector on each end and a hulking big ground connection on the can. Inside was a spark gap with dime-sized silver contacts, and a few turns of copper busbar as an inductor to smooth out the spike that got past the spark gap. That goes where the cable enters the building. Similar units today tend to be smaller. There will still be serious metal boxes.[1] You need a serious ground. As in hulking big copper cable to a long ground rod. Grounding to a pipe is no longer allowed; there might be plastic pipe somewhere in the system, either now or in the future. The next stage is a "central office protector". This is a gas tube with three terminals - both sides of the line, and ground. So it's an enclosed spark gap in an inert gas. An overvoltage will ionize the gas and short it to ground. Telco central offices have one of those on each line. They're plug-in devices that sometimes have to be replaced. There's a lot of obviously fake stuff on eBay and Amazon in this area. 2D logos superimposed on curved surfaces, even. There's a standard, UL 497B. If it doesn't have that certification, don't buy. [1] https://www.polyphaser.com/search?Category=Data+Surge+Protectors&sort=y&view_type=grid https://www.polyphaser.com/search?Category=Data+Surge+Protec... [1] http://www.arrl.org/lightning-protection http://www.arrl.org/lightning-protection
  - 4y ago